A fluid dispensing apparatus operates to dispense precise volumes of fluid onto a substrate or workpiece during a manufacturing process. The dispensed fluid may include viscous material such as solder flux, solder paste, adhesives such as hot melt adhesive, solder mask, thermal compounds, oil, encapsulants, potting compounds, inks, and silicones. Conventionally, these fluid dispensing apparatus include a moveable valve member that rapidly moves in a reciprocating manner towards and away from contact with a valve seat located in a nozzle. The nozzle is typically formed from a non-resilient material such as a metal, and the nozzle includes a passageway in communication with an outlet of the fluid dispensing apparatus. During the rapid movement towards the valve seat, the moveable valve member forces the precise volume of fluid into the passageway and thereafter through the outlet onto the substrate or workpiece thereby “jetting” the precise volume out of the fluid dispensing apparatus.
Some conventional fluid dispensing apparatus of this type have certain drawbacks. For example, when a volume of the fluid breaks off from the outlet onto the substrate or workpiece, some fluid may remain on or around the outlet, which can harden over time and thereby impede or affect the accurate dispensing of further fluid volumes from the fluid dispensing apparatus. Moreover, upon contacting the valve seat in a non-resilient nozzle, the moveable valve member typically experiences a recoil movement by which temporarily recoils or “bounces” away from the valve seat before returning to contact with the valve seat. This recoil movement may force undesired small amounts of additional fluid towards the outlet and, as a result, to the substrate or workpiece. Such additional fluid may also remain on or around the outlet and harden over time as set forth above. In addition, when the moveable valve member approaches contact with the valve seat in these conventional designs, some fluid is forced back into the dispensing apparatus and some fluid is forced to move towards and through the discharge outlet. This split of the fluid in these two directions can vary slightly for each dispensing cycle, which means it is difficult to dispense a truly fixed and repeatable volume in each dispensing cycle, even with careful control of the actuation of the moveable valve member.
Therefore, it is desirable to provide a fluid dispensing apparatus that overcomes these and other deficiencies of conventional fluid dispensing apparatus, as described herein.